| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.vxquery.compiler.rewriter.rules; |
| |
| import org.apache.commons.lang3.mutable.Mutable; |
| import org.apache.vxquery.compiler.rewriter.rules.util.ExpressionToolbox; |
| import org.apache.vxquery.functions.BuiltinOperators; |
| import org.apache.vxquery.functions.Function; |
| |
| import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException; |
| import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression; |
| import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator; |
| import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext; |
| import org.apache.hyracks.algebricks.core.algebra.base.LogicalExpressionTag; |
| import org.apache.hyracks.algebricks.core.algebra.base.LogicalOperatorTag; |
| import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression; |
| import org.apache.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression; |
| import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractLogicalOperator; |
| import org.apache.hyracks.algebricks.core.algebra.operators.logical.UnnestOperator; |
| |
| /** |
| * The rule searches for an unnest operator (1) immediately following an unnest |
| * operator (2). XQuery unnest operator (1) must have a scalar implementation |
| * of the unnest function. If so the two unnest expressions can be merged |
| * together. |
| * |
| * <pre> |
| * Before |
| * |
| * plan__parent |
| * UNNEST( $v2 : uf2( $v1 ) ) |
| * UNNEST( $v1 : uf1( $v0 ) ) |
| * plan__child |
| * |
| * Where $v1 is not used in plan__parent and uf1 is not a descendant expression. |
| * |
| * After |
| * |
| * plan__parent |
| * UNNEST( $v2 : uf2( sf1( $v0 ) ) ) |
| * plan__child |
| * |
| * uf1 becomes sf1 since it changes from unnesting to scalar expression. |
| * </pre> |
| * |
| * @author prestonc |
| */ |
| public class ConsolidateUnnestsRule extends AbstractUsedVariablesProcessingRule { |
| |
| protected boolean processOperator(Mutable<ILogicalOperator> opRef, IOptimizationContext context) |
| throws AlgebricksException { |
| AbstractLogicalOperator op = (AbstractLogicalOperator) opRef.getValue(); |
| if (op.getOperatorTag() != LogicalOperatorTag.UNNEST) { |
| return false; |
| } |
| UnnestOperator unnest1 = (UnnestOperator) op; |
| |
| AbstractLogicalOperator op2 = (AbstractLogicalOperator) unnest1.getInputs().get(0).getValue(); |
| if (op2.getOperatorTag() != LogicalOperatorTag.UNNEST) { |
| return false; |
| } |
| UnnestOperator unnest2 = (UnnestOperator) op2; |
| |
| if (usedVariables.contains(unnest2.getVariable())) { |
| return false; |
| } |
| |
| // Check to see if the unnest2 expression has a scalar implementation. |
| ILogicalExpression logicalExpression2 = (ILogicalExpression) unnest2.getExpressionRef().getValue(); |
| if (logicalExpression2.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) { |
| return false; |
| } |
| AbstractFunctionCallExpression functionCall2 = (AbstractFunctionCallExpression) logicalExpression2; |
| Function functionInfo2 = (Function) functionCall2.getFunctionInfo(); |
| if (!functionInfo2.hasScalarEvaluatorFactory()) { |
| return false; |
| } |
| // Exception for specific path expressions. |
| if (functionCall2.getFunctionIdentifier().equals(BuiltinOperators.DESCENDANT.getFunctionIdentifier()) |
| || functionCall2.getFunctionIdentifier().equals( |
| BuiltinOperators.DESCENDANT_OR_SELF.getFunctionIdentifier())) { |
| return false; |
| } |
| |
| // Find unnest2 variable in unnest1 |
| Mutable<ILogicalExpression> unnest1Arg = ExpressionToolbox.findVariableExpression(unnest1.getExpressionRef(), |
| unnest2.getVariable()); |
| if (unnest1Arg == null) { |
| return false; |
| } |
| |
| // Replace unnest2 expression in unnest1 |
| ScalarFunctionCallExpression child = new ScalarFunctionCallExpression(functionInfo2, |
| functionCall2.getArguments()); |
| unnest1Arg.setValue(child); |
| |
| // Move input for unnest2 into unnest1 |
| unnest1.getInputs().clear(); |
| unnest1.getInputs().addAll(unnest2.getInputs()); |
| return true; |
| } |
| } |